Here is the 1st official Doc Savage cover done by Bob Larkin. This August 1937 pulp story was originally titled "Ost". The Bantam book was published in July 1977.
This is a very striking cover, although Doc is presented as being older. Bob would continue to do the most Doc Savage paperback covers of any artist.
As Bob was a big Doc Savage fan growing up, he was very ecstatic when Len Leone, the Bantam Art Director, gave him the assignment.